Lightweight ceramic article and method of making the same



J1me 1935. B. TOWNSHEND 2,003,319

LIGHTWEIGHT CERAMIC ARTICLE AND METHOD OF MAKING THE SAME Filed Dec. 13, 1952 INVENTOR Bailqy Towns/amt ATTORNEY Patented June 4, 1935 LIGHTWEIGHT GERAMIIG ARTICLE AND METHOD @F MAKING THE SAW Bailey Townsliend, Westfield, N. .1, assignor to Johns-Manville @orporation, New York, N. Y, a corporation of New York Application December 13, W32, Serial No. 646,962

This invention relates to a lightweight ceramic a ceramic binding material, and water, shaping article and a method of manufacturing the same. the mixture and removing any excess of water The invention relates particularly to such an therefrom, as by suitable mechanical means, article provided with voids that are partly filled preferably either at very low pressure or without with fibrous filling material, such as rock wool, or the use of any pressure at all, drying and then 5 the like. firing the shaped mixture to develop a ceramic It is an object of the invention to provide a dubond and produce a rigid article provided with rable, washable, fireproof article of manufacture voids. When the product is to be used for absorbthat is effective in absorbing incident sound and ing sound, a destructible, pore-forming filler may in thermal insulation up to temperatures of apbe incorporated with the other ingredients in the 10 proximately 2100" F. and to provide a convenient, original mixture and destroyed during the firing relatively inexpensive, and novel method of manoperation. The process is illustrated in more deufacture. Other objects and advantages of thetail in the following specific examples, which are invention will appear from the detailed descripmodifications of the general method.

tion that follows. a 15 The invention is illustrated by the following Emamme description and by the drawing in which The fibrous material used consists of rock wool.

Fig. l is a perspective view of an embodiment This product is made by a method that includes or the invention. melting argillaceous limestone or the like, al-

2o Fig. 2 is a cross sectional view of a modified lowing it to flow from a small orifice, in a small structure provided with additional capillaries or stream, and blowing, into a receiving chamber, pores extending from voids within the article to by means or" steam in the presence of a small an exterior surface thereof. proportion of oil, to coat the individual fiber Fig. 3 is an exterior view of an aggregation of The form which I use is so-called ncrlulated rock heat-resistant fibrous material suitable for use wool, which results from passing fibers, made 25 in compositions of the invention. as described, between thresher rollers, to give In the various figures like reference characters small aggregations of fibers, then collecting the denom like parts. said aggregations and tumbling them. in a ro= Thus, i denotes a heat-resistant fibrous matetating device provided with screen walls, say

rial, such as mineral wool including, for example, with 7 meshes to the linear inch; fine material 3o slag wool, glass wool, or, preferably, rock wool in or shot-like particles are removed through the the form of void-containing aggregations or clusscreen walls and the rock wool fibers retained tors. The fibrous material should be heat-rewithin the tumbler are rolled into more or sistant to the extent of not losing its form entirely round clusters or nodules. The product is a -ireeduring firing of the article containing it. The ly flowing, granular material consisting essen- 35 binder material 2 is ceramic, is disposed between tially of irregular spheroidal particles of aver= the clusters of fibers and, in the finished article, age diameter that may be about on iourth inch. is fired to form a firm, ceramically bond-ed ma The binding material used comprises a clay trix between the aggregations or clusters and give that, on being fired, matures to gi e a ce-= rigidity to the article. The finished article reramic bond, at a temperature belo of @911- do tains voids present initially in the fibrous clusters plete fusion or decomposition of i e rock wool, and may be provided also with numerous small say, at about 2006 Thus, Ros hain (it. capillaries or pores 3, which communicate with an ball clay has been used satisfact exterior surface of the article and with the voids The fibers and clay are made i in the fibrous material. In the structure shown mixture with water and the mixture is shaped. 45

in Fig. 2, there appear additional pores 3, result- For example, l. part by weight of the lightly ing from the escape of a gas or the destruction of oiled, nodulated rock wool is stirred into a th a filler material during making of the article, and ture with 1 part of the clay and then. uniformly also isolated cells 5 representing, for example, wetted with l parts water. The resulting enclosed bubbles of gas. The pores 3 and cells 5, wet mixture is shaped by being cast in molds so in the figures, are somewhat enlarged in relation provided with a screen bottom and removable to the rest oi the structure. sides. After the excess of water drained In general, the products of the invention maybe away, say after a few minutes, the sides oi made by a process which comprises forming a mold are removed and the shaped mixture, sup= mixture including nodulated rock wool or the like, ported on the screen, is dried at an elevated -used to advantage firing temperatures of approximately 2000 to 2100 F.

A product so made had an overall density of approximately 29 lbs. per cu. ft. and a modulus of rupture of 95. With varying proportions of ingredients, products may be made of a density of 20 to 40 lbs. per cu. ft. and modulus of rupture of 50 to 200 lbs. per sq. in.

Example II The procedure of Example I is followed, with the exception that the nodulated rock wool used is made water-resistant by being thoroughly coated with aluminum stearate or other waterrepellent material, such as zinc stearate or a wax, before the wool is mixed with the other ingredients of the composition. The waterproofing material may be applied in dust form and then spread over the fibers by melting and tumbling, or, the waterproofing material may be applied in the form of a solution in a volatile solvent, which solvent is then evaporated.

With such water-resistant fibers, less water is necessary to form a mixture for casting. Thus, there has been used only 2.8 parts by weight of water for a mixture of 1 part of rock wool and 1 part of clay.

Example III The procedure of Example I is modified by the incorporation, into the original mixture, of

a combustible material adapted to be destroyed during firing of the product and thus to produce additional voids. The gas produced during the destruction of the filler may increase the porosity by development of gas-escape channels communicating with an exterior surface of the finished article.

There is made a mixture of 31 parts by weight of lightly oiled and nodulated rock wool, a small proportion, say 6 parts by weight, of a filler that is destructible by heat with the development of gas, suitably cork in the form of granules or sawdust, say of size such that the particles may be passed through a 4-mesh screen and be retained on a IO-mesh screen, 53 parts of Rockingham ball clay, 9 parts of a red burning clay that develops a good ceramic bond at about 2000 to 2100 F., and sufficient water to give a plastic mixture suitable for casting. The mixture is cast, drained to remove excess water, dried and fired, as described above. The firing should not be so rapid as to cause gas developed by the Example IV The procedure of Example III is modified in that the combustible filler material incorporated initially and later destroyed, during firing of the product, is of elongated form and, therefore, adapted to produce elongated voids.

For example, the filler may consist of fine excelsior or very fine curled wood shavings, hay, short lengths of broom straw or the like. Curled or irregularly shaped material that does not tend to pack together and that maintains its several units in spaced relationship to each other are preferred to material composed of straighter members.

The heat-destructible, elongated fibrous filler may be substituted for cork and the resulting composition treated as described under Example III.

During firing of the article, say at approximately 2000 to 2100 F., the fibers are decomposed, to leave elongated voids corresponding to positions initially occupied by the fibers and interconnecting the voids within the rock wool clusters. Also, gas of decomposition is formed and, in escaping, forms gas escape channels communicating with an exterior surface of the article.

Ezcample V The procedure of Example I is modified by the incorporation of a composition adapted to develop gas in the presence of water. This gas, in escaping, produces gas escape channels. Thus, the nodulated wool is soaked in a dilute solution of aluminum sulfate, dilute sulfuric acidv or other suitable acidic material. The soaked wool is mixed with the clay and then, quickly, with an aqueous mixture containing a carbonate, say with an aqueous suspension of precipitated calcium carbonate or of ground dolomite. The

mixture is promptly cast anddrained, to produce a shaped mixture provided with voids within the clusters or nodules of fibrous material and also gas escape channels or pores 4 (Fig. 2) connecting the voids with an exterior surface. The mixture is then dried and fired with preservation of the said voids and pores.

Example VI The procedure of Example I is followed except that there is used a density-reducing agent in addition to the rock wool. For example, the water used in forming the original mixture of fibers, clay, and water contains saponin or other foam stabilizer and air, or other suitable gas, dispersed in the form of fine bubbles.

When such a foam is used, there is made a finished product containing voids and pores and also isolated cells 5 which correspond to individual bubbles in the foam used. Many of these cells are not in communication with the other voids or pores or with an exterior surface and are very efiective in thermal insulation.

Other density-reducing agents than a foam or the heat-destructible filler, of Examples III and IV, may be used.

Regardless of the particular modification of the method of manufacture that may be used, the products of the present invention have a number of interesting features.

During the mixing and shaping operations the clusters of fibers retain voids. After casting and draining away of any excess water, the fibers reenforce the mixture and thus decrease the liability of the cast product to breakage. The product made, for example, as described under Example I, is light in weight, strong, and an effective thermal insulating material. Thus, a

(Bill aooaaie product weighing 28 pounds per cu. ft. has a modulus of rupture of 110 lbs. per sq. in. and a thermal conductivity at a mean temperature of 285 F. of 0.81 B. t. u./sq. ft./inch./ F. per hr. Such a product is suitable for use at temperatures up to 2100 F. or above, say to the temperature at which the product was originally fired, with preservation of the shape or fibrous structure of the material within the voids. The fact that the voids in the finished product are partly filled with fibrous material makes these voids more efiective in thermal insulation than voids of the same size would be if not so filled in part.

The products of the present invention, when first removed from the firing operation, have surfaces that are not absolutely regular. If desired, the products may be submitted to a cutting or polishing operation to remove the exterior surfaces and produce approximately the exact size and shape desired. Although the prodnets are firm and rigid, they are adapted to be machined readily and lend themselves readily to the sizing operation.

It is not necessary to the invention to explain all of the unexpected results obtained. It is interesting, however, to note that the development of the capillaries 3, that interconnect some or the voids within the several clusters of fibrous material, may be due to the shrinkage, during firing, of clay from around fibers or elongated aggregations of fibers which extend from one cluster to another. The very high firing temperatures used causes a particularly severe shrinkage of the clay that is in contact with the rock wool fibers which themselves probably undergo incipient fusion. It is possible that the capillaries follow courses outlined originally by fibers extending from the surfaces of clusters embedded in the binding material.

The clay coating the rock wool fibers tends to preserve them under the severe conditions of firing and bonds them in the finished product.

Regardless of the correctness of any explana= tion advanced, the said capillaries 3 present in. the product and the larger pores Q resulting from the use of the destructible filler make the product readfiy permeable to incident sound. Further, the voids partly filled with fibrous materials are very efiective in destroying sound admitted thereto.

The combined result is an effective sound-absorbing unit. Thus a unit, 1 inch thick, made as described under Example Ill, with the substitution oi the (5 parts of cork there described by 12 parts of corl: filler of graded size showing 89% in the range *1 to Zli-rnesh and 20% finer than 20- mesh, has been found to weigh 28 pounds to the cubic foot and to absorb 73% of incident sound of." hi2 cycles frequency and 31% of 256 cycles.

During the firing oi" a mixture of rock wool and clay containing iron compounds or similar color producing materials, there is produced a product of considerably lighter color than would be obtained by firing the clay alone. This result, which is particularly important when making acoustical tiles for certain architectural efiects, may be due to the action of the lime content of rock wool upon the color-producing materials in the clay. In making a ceramically bonded article or selected color, comprising rock wool and clay, there may be used a clay which, when fired alone, develops a somewhat darker color than that selected.

It, on the other hand, it is desired to avoid the white color, then there may be added selected in gredients to cause the desired coloring. For example, there may be made a brown product by the use of a clay that develops a strong brown color during firing and a rock wool that is suitably colored, say, brown. The rock wool may be colored by the addition of pigmenting substances to the argillaceous limestone during the treatment preceding the blowing operation or, less advantageously, by the addition or" pigment to the fibers after blowing. For example, iron compounds may be added. Thus, the rock wool fibers, before incorporation into the clay rnixture, may be soaked in an aqueous solution of ferric chloride.

The proportions of materials used may be varied in a manner that will be evident to one skilled in the art and will depend, in part, upon properties desired in the finished product. The proportion of rock wool to clay may be increased, for example, if it is desired to make an exceptionally lightweight product. Or, the proportion of rock wool may be decreased, when it is desired to make a very strong, somewhat heavier product. The proportion of water used should be such as to facilitate shaping by the method selected.

The pressure used during the shaping operation should be such as to prevent collapse of the fibrous structure and preserve the voids therewithin.

The details that have been given are for the purpose of illustration and not restriction, and many variations therefrom may be made without departing from the spirit and scope of the invention.

What I claim is:

l. A lightweight article of manufacture comprising void-containing clusters of heat-resistant fibrous material and a ceramic binding material disposed between the said clusters and fired, to give rigidity to the article.

2. A lightweight article or" manufacture comprising void-containing clusters of heat-resistant fibrous material, an additional density-reducing agent, and a ceramic binder material.

3. A lightweight article or" manufacture com-- prising void-containing clusters mineral wool and a ceramic binding material disposed between the said clusters and fired, to give rigidity to the article.

4. A porous, li hwe ght article of manufacture comprising void-con ng nodul s of rock wool and a clay-containing ending material disposed between the said nodules ceramically bonded.

5. A porous, lightweight sound-absorbing unit comprising void-containing nodules of mineral wool and a clay-containing binding material dis= posed between the rock wool ceramicaily bonded with preservation of the voids the nodules, the said ticle being provided with pores which connect the voids with an exterior surface of the article.

6. A ceramically bonded article of manufacture provided with a plurality of voi s partly filled with fibrous filling material, capillary passageways interconnecting the said voids, and pores, of larger size the said capillary passageways, connecting the voids with an outer surface of the article, whereby the article is adapted to absorb incident sound.

'2. A ceramically bonded article of manufacture provided with a plurality or voids partly filled with fibrous filling material and provided also with pores communicating with an exterior surface of the article and with the said voids.

8. In making a ceramic product provided with voids partly filled with fibrous material, the method which comprises treating heat-resistant fibers with a water-repellent material to render the fibers water-resistant, making a plastic mixture of the treated fibers, clay and water, and shaping, drying, and firing the mixture to develop a ceramic bond, with preservation of the shape of approximately the original fibers.

9. The herein described method of making a lightweight article which comprises forming a mixture including void-containing clusters of heat-resistant fibers, clay, and water, shaping the mixture and removing'any excess of water therefrom, and drying and firing the shaped mixture to develop a ceramic bond in the clay and produce a rigid article with preservation of voids within the said clusters.

10. The herein described method of making a lightweight article which comprises forming a mixture including fibers of mineral wool, clay, and

water, shaping the mixture and removing any excess of water therefrom, and drying and firing the shaped mixture at a temperature below that of complete fusion of the mineral wool but sufficiently elevated to develop ,a ceramic bond in the clay and produce a rigid article.

11. The herein described method of making a lightweight article which comprises forming a mixture including nodulated fibers of rock wool, clay and water, shaping the mixture and removing any excess of water therefrom, and drying and firing the shaped mixture at approximately 2000" to 2100 F.

12. The herein described method of making a lightweight article which comprises forming a mixture including fibers of mineral wool, an additional density reducing agent, clay, and Water, shaping the mixture and removing any excess of water therefrom, drying and firing the shaped mixture at a temperature below that of complete fusion of the mineral woolbut sufiiciently elevated to develop a ceramic bond in the clay.

13. The herein described method of making a porous, lightweight article which comprises forming a mixture including void-containing clusters of rock wool or the like, clay, a composition adapted to develop a gas, and then shaping,-

drying, and treating the said mixture to bond the claytherein and develop the said gas, whereby there are formed gas escape channels in the form of pores that extend from the positions occupied by the said clusters to an exterior surface of the article.

14. The herein described method of making a porous, lightweight article which comprises forming a mixture including void-containing clusters rock wool or the like, clay, a heat-destructible organic filler material adapted to develop a gas when subjected to an elevated temperature, and water, shaping and then drying and firing the mixture to produce a ceramic bond in the clay, to develop a gas from the said filler, and

cause the gas to escape, whereby there are formed gas escape channels in the form of pores that extend from the positions occupied by the said clusters to the exterior surface of the article.

15. The herein described method of making a porous, lightweight article which comprises forming a mixture including void-containing clusters of rock wool or the like, clay, elongated units of,

heat-destructible filler material adapted to develop a gas when subjected to an elevated temperature, and water, shaping and then drying and firing the mixture to produce a ceramic bond in the clay, develop a gas from the said filler, and cause the gas to escape, whereby there are formed gas escape channels in the form of pores that extend from the positions occupied by the said clusters to an exterior surface of the article.

16. The herein described method of making a lightweight article which comprises forming a mixture including fibers of rock wool, clay, and water, shaping the mixture and removing any excess of water therefrom, and drying and firing the shaped mixture at a temperature below that of complete fusion of the rock wool but sufiiciently elevated to develop a ceramic bond in the clay and produce a rigid article provided with voids between the said fibers, and subjecting the rigid article to a sizing operation to remove the exterior surface and produce approximately the exact shape and size desired.

17. In making a ceramic product provided with voids partly filled with fibrous material, the method which comprises forming water-resistant clusters of heat-resistant fibers, making a plastic mixture of the said clusters, clay and water, shaping, drying and firing the mixture to develop a ceramic bond with preservation of the fibrous material.

18. The herein described method of making a porous, lightweight article which comprises forming a mixture including heat-resistant fibrous material, clay, water and a composition adapted to develop a gas in the presence of water, shaping and then drying and firing the mixture, whereby there is formed a ceramically bonded article provided with pores extending from the positions occupied by the heat-resistant fibrous material to an exterior surface of the article.

19. In making a porous ceramic article of selected color, the method which comprises forming a mixture of rock wool, water, and a. clay adapted, when fired alone, to develop a color somewhat darker than the said selected color,

and shaping, drying and firing the said mixture.

20. In making a lightweight article, the method which comprises providing void-containing particles, applying a water-repellent material to the said particles, forming a mixture of the particles and water-repellent material with an aqueous binder composition adapted to be hardened, shaping the mixture, and then hardening the binder therein.

' BAILEY TOWNSHEND. 

